The present invention relates to a dual-mass flywheel having a first mass body and a second mass body which can rotate relative to one another by way of a damping device disposed between the first mass body and the second mass body. The damping device includes, running in the shape of an arc, at least one helical compression spring which introduces spring force into the mass bodies via contact surfaces formed on the first mass body and the second mass body. The helical compression spring is guided in the radial direction by a wall formed by a mass body. Between the wall and the helical compression spring at least one friction-reducing sliding component is provided.
A dual-mass flywheel according to this type can be used in the drive train of a motor vehicle. The drive train includes a motor, transmission, and vehicle so that the excitation of vibration by the motor also acts on the other components of the drive. In order to improve the vibration behavior and thus also the noise behavior of the drive train, dual-mass flywheels are used, which include a primary mass or a first mass body which, for example, can be rigidly connected to the crankshaft of the motor and a secondary mass or a second mass body which can rotate relative to the first mass body. The first and second mass bodies are connected to one another in a rotationally elastic manner via a damping device.
A dual-mass flywheel according to this type has been disclosed, e.g., based on DE 10 2007 003 047 A1. The mass body of this known dual-mass flywheel is supported via helical compression springs and, in fact, via contact surfaces provided on the mass bodies.
This known dual-mass flywheel is formed so that the sheet metal parts forming the receiving chamber for the helical compression springs are formed with low wall thicknesses to reduce weight and the helical compression springs are supported against the sheet metal parts via sliding shoes. The introduction of compressive forces into the sheet metal parts is done via impact components formed in the manner of a flange. Via the sliding shoes between the helical compression springs and the sheet metal parts, the result is supposed to be achieved that the spring ends do not dig through the sheet metal parts.
In other words, this means that additional parts are present in the form of the sliding shoes. The additional parts are intended to ensure that the friction between the helical compression spring and a wall guiding the helical compression spring is reduced. The helical compression springs are namely massive parts which at high angular speed of the dual-mass flywheel are pressed against the wall with great centrifugal force.
Due to the great centrifugal force, lubricants present in the channel guiding the helical compression spring are pressed out of the contact area between the helical compression spring and the wall, which leads to the result that the friction between the wall and the helical compression spring increases so much that the helical compression spring behaves as a rigid body element and thus the desired acoustic decoupling between the drive motor and the drive train of the vehicle is no longer present.
The sliding shoes present in the known dual-mass flywheel described above are made of a plastic material, which due to the relative movement between the helical compression spring and the wall is, so to speak, rubbed to pieces and thus can no longer exercise its function of reducing friction. The plurality of sliding shoes present in the known dual-mass flywheel also leads to a significant and undesirable increase in cost of the dual-mass flywheel.
In view of the above, there is therefore needed a dual-mass flywheel of the above type such that its function of reducing friction between the helical compression spring and the wall is maintained even for a longer operating period and thus the acoustic decoupling between the motor and the drive train is retained.
This need is met according to the invention by providing a dual-mass flywheel with a first mass body and a second mass body which can rotate relative to one another via a damping device disposed between the first mass body and the second mass body. The damping device includes, extending in the shape of an arc (curved), at least one helical compression spring which introduces spring force into the mass bodies via contact surfaces formed on the first mass body and the second mass body. The helical compression spring is guided in the radial direction by a wall formed by one mass body. Between the wall and the helical compression spring, at least one friction-reducing sliding component is provided, where a wire cushion body is provided as a sliding component.
With this dual-mass flywheel, a configuration is created which is substantially more stress-resistant than the plastic sliding shoes of the known dual-mass flywheels described above which are made of a plastic material. The helical compression spring under centrifugal force no longer directly abuts the wall but rather with the interposition of a wire cushion body, at least in sections along the longitudinal direction of the helical compression spring.
The wire cushion body has a spring action which, depending on in which direction it is packed more or less densely, can be configured differently. Thus, the wire cushion body can be formed to be elastic in the longitudinal direction and/or in the radial direction of the helical compression spring. The wire cushion body has cavities in which lubricants in the form of grease or the like can be embedded.
Due to the spring action of the wire cushion body it is, under the load of centrifugal force on the helical compression spring, in fact compressed in the radial direction relative to the longitudinal axis of the dual-mass flywheel but, with an appropriately chosen rigidity of the wire cushion body, the cavities are preserved in the radial direction and thus also the lubricants present between the wire cushion body and the wall of the dual-mass flywheel. Due to the laminar abutment of the wire cushion body against the wall, the contact pressure per unit area between the wire cushion body and the wall is significantly less than the contact pressure per unit area between the coils of the helical compression spring and the wall when the helical compression spring abuts the wall directly.
Care must also be taken when forming the wire cushion body that lubricants are embedded in the matrix of the wire cushion body which, even at a high angular speed of the dual-mass flywheel, remain present in the area of contact between the wire cushion body and the wall and thus retain their friction-reducing action even for longer periods of operation of the dual-mass flywheel according to the invention.
The wire cushion body can, for example, be a body formed of knitted wire fabric, where the body is compressed in a mold by a pressing process. Along with this, the wire cushion body can also be formed by a wound body which is wound in layers on a shaft or a spool. Before the wire in this case is subjected to the winding process, it is subjected, at least within partial segments or sections along its length, to a preliminary deformation, which leads to the result that the individual wire sections within the layers and also between the layers intertangle with one another significantly better and more intensively than is the case with wire which has not been deformed. This leads to a wire cushion body which is significantly more stress-resistant than a wire cushion body made of wire which has not been deformed.
In connection with this, it is provided according to an extension of the invention that the wire cushion body is formed to be elastic in the longitudinal direction and/or in the radial direction of the helical compression spring. Depending on how densely the wire cushion body is packed in the radial direction, it is possible to achieve rigidity of the wire cushion body in its radial direction. With this, for example, a configuration is possible in which the relative movement between the spring and the wire cushion body is greater than the relative movement between the wire cushion body and the wall of the dual-mass flywheel.
The wire cushion body can also be formed to be elastic in the longitudinal direction of the helical compression spring so that in a spring movement of the helical compression spring, e.g., in the radially inward-lying area of contact between the helical compression spring and the wire cushion body, the spring movement is reproduced, taken up so to speak, by the wire cushion body in the radially outward-lying area between the wire cushion body and the wall of the dual-mass flywheel, but a relative movement no longer takes place or takes place only to a slight degree.
In such a configuration, care is therefore taken that the helical compression springs can move almost freely and thus hardening of the helical compression springs is avoided and thus the desired acoustic decoupling is retained.
According to one embodiment of the present invention, it is provided that the wire cushion body is disposed as an elongated insert between at least one partial area of the length of the helical compression spring and the wall. In other words, this means that it can even be sufficient if the wire cushion body only separates partial areas of the length of the helical compression spring and the wall from one another. However, an arrangement of the wire cushion body as an insert between the helical compression spring and the wall and along the entire length of the helical compression spring running in the shape of an arc is provided according to the invention.
According to a different embodiment of the present invention, it is provided that the wire cushion body is formed as a mantle which envelopes the helical compression spring, at least along a partial area of its length. With this the helical compression spring, so to speak, plugs into the wire cushion body formed as a mantle and in fact at least at partial areas of its length. However, a complete envelopment of the helical compression spring along its entire length by the wire cushion body in the form of a mantle is also provided according to the present invention.
According to an extension of the invention, it is provided that the wire cushion body includes, in the area of one end facing a contact surface, a wire cushion counterbearing body formed as one piece with the wire cushion body or disposed thereon. The wire cushion counterbearing body is provided between one spring end of the helical compression spring and the contact surface. An introduction of spring force into the contact surface takes place via the wire cushion counterbearing body.
The wire cushion counterbearing body can therefore, for example, be inlaid at the end of the wire cushion body or also can be formed together with the wire cushion body during the manufacture of the wire cushion body. The wire cushion counterbearing body then leads to a reduction of wear of the contact surface on the dual-mass flywheel and thus to an extension of the service lifetime of the dual-mass flywheel.
It is also possible in this way to reduce the contact surface since the wire cushion body, unlike the spring end of the helical compression spring, lies over the surface of the contact surface and thus the contact pressure per unit area of the contact surface is reduced. This can also be utilized to reduce the contact surface, whereby a reduction of the dimensions of the components is made possible and thus an advantage in weight is achieved.
The wire cushion counterbearing body can also be provided at a distance from the spring end or from the contact surface so that initially a relatively free mobility of the helical compression springs is achieved and only after a predetermined excursion of the spring is contact between the spring end of the helical compression spring and the wire cushion counterbearing body reached. In general, an improved insulation against vibration can be achieved with the wire cushion counterbearing body between the spring end and the contact surface and thus an improvement of the acoustic behavior of the dual-mass flywheel according to the invention with respect to the known dual-mass flywheel.
According to an extension of the invention, it is provided that the wire cushion body is formed by at least two wire cushion segment bodies which are disposed functionally in a row or in parallel.
Through the connection in a row a soft configuration of the wire cushion body is achieved while through the connection in parallel a wire cushion body can be formed which has a spring characteristic with greater rigidity and thus a harder wire cushion body, depending on which configuration is desired for a given application.
According to an extension of the invention, it is also provided that the wire cushion body is formed along its direction of action with a linear or progressively or regressively variable spring rate. Such a configuration with a variable spring rate can, for example, be achieved in the manufacture of the wire cushion body by forming the wire cushion body with a predetermined number of cavities, which leads to the number of cavities corresponding to a softer or harder configuration. A progressive spring rate can, for example, be of advantage when, depending on the spring excursion of the wire cushion body, flexible behavior is desired initially in order to achieve, after a predetermined spring excursion, an increase of the spring characteristic and thus a harder behavior of the wire cushion body.
The wire cushion body can be formed of metallic, ceramic, or vitreous materials, of polymers, or of mixtures thereof. Also, the wire cushion body can be formed of metallic materials of different hardness. With this a configuration is made possible in which the wire cushion body has a first contact area of a soft metallic material which is then followed by a second contact area of a harder metallic material, whereby, for example, a configuration deviating from a linear spring rate is possible.
The wire cushion body provided according to the invention in the dual-mass flywheel can have cavities in which a lubricant is embedded. It can also have embedded solid lubricant parts, each of which provides that the friction between the wire cushion body and the wall of the dual-mass flywheel remains low and thus hardening of the helical compression springs is prevented.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawing.